Cancer comprises a group of malignant neoplasms that can be divided into two categories, carcinoma, comprising a majority of the cases observed in the clinics, and other less frequent cancers, which include leukemia, lymphoma, central nervous system tumours and sarcoma. Carcinomas have their origin in epithelial tissues while sarcomas develop from connective tissues and those structures that had their origin in mesoderm tissues. Sarcomas can affect, for instance, muscle or bone and occur in the bones, bladder, kidneys, liver, lung, parotid or spleen.
Cancer is invasive and tends to metastasise to new sites. It spreads directly into surrounding tissues and also may be disseminated through the lymphatic and circulatory systems. Many treatments are available for cancer, including surgery and radiation for localised disease, and drugs. However, the efficacy of available treatments on many cancer types is limited, and new, improved forms of treatment showing clinical benefit are needed.
This is especially true for those patients presenting with advanced and/or metastatic disease. It is also true for patients relapsing with progressive disease after having been previously treated with established therapies for which further treatment with the same therapy is mostly ineffective due to acquisition of resistance or to limitations in administration of the therapies due to associated toxicities.
Chemotherapy plays a significant part in cancer treatment, as it is required for treatment of advanced cancers with distant metastasis and often helpful for tumor reduction before surgery, and many anti-cancer drugs have been developed based on various modes of action.
The ecteinascidins are marine alkaloids and some of them possess potent in vitro antitumour activity. Several ecteinascidins have been reported previously in the patent and scientific literature.
For example, U.S. Pat. No. 5,089,273 describes novel compositions of matter extracted from the tropical marine invertebrate, Ecteinascidia turbinata, and designated therein as ecteinascidins 729, 743, 745, 759A, 759B and 770. These compounds are useful as antibacterial and/or antitumour agents in mammals.
U.S. Pat. No. 5,256,663 describes pharmaceutical compositions comprising matter extracted from the tropical marine invertebrate, Ecteinascidia turbinata, and designated therein as ecteinascidins, and the use of such compositions as antibacterial, anti-viral, and/or antitumour agents in mammals.
U.S. Pat. No. 5,478,932 describes ecteinascidins isolated from the Caribbean tunicate Ecteinascidia turbinata, which provide in vivo protection against P388 lymphoma, B16 melanoma, M5076 ovarian sarcoma, Lewis lung carcinoma, and the LX-1 human lung and MX-1 human mammary carcinoma xenografts.
U.S. Pat. No. 5,654,426 describes several ecteinascidins isolated from the Caribbean tunicate Ecteinascidia turbinata, which provide in vivo protection against P388 lymphoma, B16 melanoma, M5076 ovarian sarcoma, Lewis lung carcinoma, and the LX-1 human lung and MX-1 human mammary carcinoma xenografts.
U.S. Pat. No. 5,721,362 describes a synthetic process for the formation of ecteinascidin compounds and related structures.
Further background is to be found illustratively in: Corey, E. J., J. Am. Chem. Soc., 1996, 118 pp. 9202-9203; Rinehart, et al., Journal of National Products, 1990, “Bioactive Compounds from Aquatic and Terrestrial Sources”, vol. 53, pp. 771-792; Rinehart et al., Pure and Appl. Chem., 1990, “Biologically active natural products”, vol. 62, pp. 1277-1280; Rinehart, et al., J. Org. Chem., 1990, “Ecteinascidins 729, 743, 745, 759A, 759B, and 770: Potent Antitumour Agents from the Caribbean Tunicate Ecteinascidia turbinata”, vol. 55, pp. 4512-4515; Wright et al., J. Org. Chem., 1990, “Antitumour Tetrahydroisoquinoline Alkaloids from the Colonial Ascidian Ecteinascidia turbinata”, vol. 55, pp. 4508-4512; Sakai et al., Proc. Natl. Acad. Sci. USA 1992, “Additional antitumour ecteinascidins from a Caribbean tunicate: Crystal structures and activities in vivo”, vol. 89, 11456-11460; Science 1994, “Chemical Prospectors Scour the Seas for Promising Drugs”, vol. 266, pp. 1324; Koenig, K. E., “Asymmetric Synthesis”, ed. Morrison, Academic Press, Inc., Orlando, Fla., vol. 5, 1985, p. 71; Barton, et al., J. Chem. Soc. Perkin Trans., 1, 1982, “Synthesis and Properties of a Series of Sterically Hindered Guanidine Bases”, pp. 2085; Fukuyama et al., J. Am. Chem. Soc., 1982, “Stereocontrolled Total Synthesis of (+)-Saframycin B”, vol. 104, pp. 4957; Fukuyama et al., J. Am. Chem. Soc., 1990, “Total Synthesis of (+)-Saframycin A”, vol. 112, p. 3712; Saito, et al., J. Org. Chem., 1989, “Synthesis of Saframycins. Preparation of a Key Tricyclic Lactam Intermediate to Saframycin A”, vol. 54, 5391; Still, et al., J. Org. Chem., 1978, “Rapid Chromatographic Technique for Preparative Separations with Moderate Resolution”, vol. 43, p. 2923; Kofron, W. G.; Baclawski, L. M., J. Org. Chem., 1976, vol. 41,1879; Guan et al., J. Biomolec. Struc. & Dynam., vol. 10 pp. 793-817 (1993); Shamma et al., “Carbon-13 NMR Shift Assignments of Amines and Alkaloids”, p. 206 (1979); Lown et al., Biochemistry, 21, 419-428 (1982); Zmijewski et al., Chem. Biol. Interactions, 52, 361-375 (1985); Ito, CRC CRIT. Rev. Anal. Chem., 17, 65-143 (1986); Rinehart et al., “Topics in Pharmaceutical Sciences 1989” pp. 613-626, D. D. Breimer, D. J. A. Cromwelin, K. K. Midha, Eds., Amsterdam Medical Press B. V., Noordwijk, The Netherlands (1989); Rinehart et al., “Biological Mass Spectrometry”, 233-258 eds. Burlingame et al., Elsevier Amsterdam (1990); Guan et al., Jour. Biomolec. Struct. & Dynam., vol. 10 pp. 793-817 (1993); Nakagawa et al., J. Amer. Chem. Soc., 111: 2721-2722 (1989); Lichter et al., “Food and Drugs from the Sea Proceedings” (1972), Marine Technology Society, Washington, D.C. 1973, 117-127; Sakai et al., J. Amer. Chem. Soc. 1996, 118, 9017; Garcia-Rocha et al., Brit. J. Cancer, 1996, 73: 875-883; and Pommier et al., Biochemistry, 1996, 35: 13303-13309.
In particular, ecteinascidin 743 has been found also to exhibit promising action when tested in animal models, as, for example, when evaluated against xenografts of breast cancer, non-small cell lung, melanoma and ovarian cancer.
A paper on in vitro antitumour activity of the novel marine agent, Ecteinascidin-743 (ET-743, NSC-648766) against human tumours explanted from patients, Annals of Oncology, 9: 981-987, 1998, is typical of the in vivo reports. The authors conclude from their data that continuous or protracted exposure may enhance activity. In the same issue of that journal at pages 989-993, a paper on in vitro schedule-dependency of myelotoxicity and cytotoxicity of Ecteinascidin 743 (ET-743) concludes that prolonged exposure might represent the best schedule of administration.